Sides

Directions:

Step 1.

Place 2 tablespoons butter in a large saucepan and heat over medium heat. Add leeks and saute until softened but not browned, about 4 to 5 minutes.

Step 2.

Add cream and milk to the saucepan and heat until mixture simmers.

Step 3.

Add salt and white pepper, stirring well to combine.

Step 4.

Peel potatoes and place a mandoline across the top of the saucepan. Slice potatoes into 1/8-inch thick slices directly into hot cream mixture. Press potato slices gently with a silicone spatula to submerge.

Step 5.

Cook, undisturbed, until potatoes are partially cooked and mixture begins to thicken, about 10 to 12 minutes. Stir in 3 tablespoons thyme leaves.

Step 6.

Preheat oven to 375degF and place a rack in the center. Generously grease a 13 x 9 x 2-inch baking dish with butter.

Step 7.

Combine cheeses in a small mixing bowl. Using a slotted spoon or spider, carefully transfer the potato slices to the prepared baking dish.

Step 8.

Carefully pour enough cream mixture to barely cover potatoes. Dot with remaining 2 tablespoons butter and cover with remaining cheese mixture.

Step 9.

Bake in preheated oven until casserole bubbles around the edges, potatoes are tender and the top is golden brown, about 50 to 60 minutes.

Step 10.

If the top begins to brown too deeply before potatoes are cooked, cover gratin with aluminum foil.

Step 11.

If the top has not browned when potatoes are cooked, place gratin under a preheated broiler for 2 to 3 minutes, continuously watching to ensure it doesn't burn.

Step 12.

Allow gratin to sit for at least 20 minutes before serving.